This invention relates to an improvement in a froth flotation process for concentration and separation of metallic sulfide mineral ores. The improved process is directed to separations wherein a mercaptan is utilized as a collector in an earlier flotation stage. The improved method of this invention includes the addition of activated carbon to achieve deactivation of the mercaptan prior to a mineral separation stage and to achieve enhanced separation of the metallic elements desired.
Froth flotation is a process commonly employed for separating, collecting, and, hence, concentrating valuable minerals, particularly sulfide and oxide ores, from the gangue minerals associated with these minerals in their ores. The usual steps are as follows:
(a) The ore is crushed and subjected to wet grinding to provide a pulp wherein the ore particles are typically reduced to minus 48 mesh and with about 50% of the particles being in the minus 200 mesh fractions.
(b) The ore pulp is generally diluted with water to approximately 30% solids by weight.
(c) Various conditioning, collecting, and frothing agents are then added to the mineral pulp.
(d) The pulp is then aerated to produce air bubbles that rise to the surface of the pulp and to which the desired mineral particles selectively attach themselves by virtue of the characteristics of the collectors employed, thereby permitting removal of these minerals in a concentrated form.
There are, of course, numerous patents on processes for froth flotation concentration and separation of minerals. One such patent is U.S. Pat. No. 2,559,104 (issued July 3, 1951) to Arbiter et al which relates to a flotation recovery method for molybdenite. Arbiter et al teaches a specific system in which a collector is oxidized prior to subsequent separation stages. The problem addressed in the Arbiter et al patent involves reducing excess further and excess collector inthe subsequent cleaning stage. They tend to collect by virtue of the fact that the bulk of the collector and frother are carried forward into the next cleaning stage. In the Arbiter et al patent, reduction of the excess frother is accomplished by the addition of the activated carbon as required.
U.S. application Ser. No. 852,413, filed Nov. 17, 1977 by Adrian Wiechers, now U.S. Pat. No. 4,211,644 (the specification and claims of which are specifically incorporated herein by reference) teaches an improved process utilizing a mercaptan as a collector, the preferred mercaptan being normal dodecyl mercaptan ("DDM"). As will be seen hereinafter, the use of DDM increases the overall copper recovery from the ore, but at the same time can make separation of the copper from the molybdenite more difficult.